The latest, at a naval college in Lahore Tuesday, was the fourth in five days.
Attacks aren't just a US concern, more Pakistanis say.
The president cast himself as Pakistan's best bet for stability in a nine-day visit.
Director of CIA says "no reason" to doubt Islamist group's responsibility, echoing findings of Scotland Yard.
The attack is a setback for the Army and is raising concerns ahead of next month's elections.
One tribal leader vows to raise a force of 600 to help fight an Al Qaeda-linked tribe in Waziristan.